Field of the Invention
The present invention relates to a signal transmission circuit, and more particularly to a line driver for transmitting an ECL logic signal over a 2-wire balanced line interconnecting printed circuit boards or devices.
In a recent high-speed computer system, an emitter-coupled logic (ECL) is widely used, which operates transistors in a non-saturated operation area to realize high-speed switching. Meanwhile, since memory and logic circuits are now fabricated in large-scale integration (LSI) semiconductor technology and reliability of a computer system is further increased, a power failure becomes one of the main causes of a system failure.
Accordingly, a line driver which is not only compatible, both electrically and in switching speed, with the ECL logic, but is reliable, i.e., which can correctly and quickly detect a power-off state developed at the sending end and inform the receiving end of such state, is in great demand.